Downhole mud motor and method of improving durabilty thereof

ABSTRACT

Disclosed herein is a downhole mud motor. The mud motor includes, a stator, a rotor in operable communication with the stator, a polymer in operable communication with the stator and the rotor, and a plurality of carbon nanotubes embedded in the polymer.

BACKGROUND

Downhole tools used in the hydrocarbon recovery industry often experience extreme conditions, such as, high temperatures and high pressures, for example. These high temperatures can be elevated further by heat generated in by the tools themselves. Mud motors, for example, can generate additional heat during operation thereof. Materials used to fabricate the various components that make up the downhole tools are therefore carefully chosen for their ability to operate, often for long periods of time, in these extreme conditions.

Many polymeric materials have maximum operating temperature ranges, that when exceeded, result in early failure of components made therefrom. Advancements in the field that allow tools to operate below these temperature ranges are well received in the art.

BRIEF DESCRIPTION

Disclosed herein is a downhole mud motor. The mud motor includes, a stator, a rotor in operable communication with the stator, a polymer in operable communication with the stator and the rotor, and a plurality of carbon nanotubes embedded in the polymer.

Further disclosed herein is a method of improving durability of a mud motor elastomer. The method includes, dissipating heat through the mud motor elastomer with carbon nanotubes embedded therein, and maintaining temperature of the mud motor elastomer below a threshold temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

FIG. 1 depicts a side view of a mud motor disclosed herein;

FIG. 2 depicts a cross sectional view of the mud motor of FIG. 1; and

FIG. 3 depicts a cross sectional view of the mud motor of FIG. 2 taken along arrows 3-3.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

Referring to FIGS. 1-3, an embodiment of a downhole mud motor 10 disclosed herein is illustrated. The mud motor 10, among other things, includes, a stator 14, a rotor 18 and a polymer 22, also referred to herein as an elastomer, positioned between the stator 14 and the rotor 18. Mud 26, pumped through the mud motor 10 flows through cavities 30 defined by clearances between lobes 34 of the stator 14 and the elastomer 22 and lobes 38 of the rotor 18. The mud 26, being pumped through the cavities 30, causes the rotor 18 to rotate relative to the stator 14 and the elastomer 22. The elastomer 22 is sealingly engaged with both the stator 14 and the rotor 18 to minimize leakage therebetween that could have a detrimental effect on the performance and efficiency of the mud motor 10. The elastomer 22, of embodiments disclosed herein, has carbon nanotubes 42 (CNT) embedded therein to increase heat transfer through the elastomer 22 and into the stator 14, the rotor 18 and the mud 26. The increased heat transfer, provided by the carbon nanotubes 42, permits temperatures of the elastomer 22 to more quickly adjust toward temperatures of matter contacting the elastomer 22 than would occur if the carbon nanotubes 42 were not present.

The operating temperature of the elastomer 22 can affect the durability of the elastomer 22. Typically, the relationship is such that the durability of the elastomer 22 reduces as the temperature increases. Additionally, temperature thresholds exist, for specific materials, that when exceeded will significantly reduce the life of the elastomer 22.

The elevated operating temperatures of the mud motor 10 are due, in part, to the high temperatures of the downhole environment in which the mud motor 10 operates. Additional temperature elevation, beyond that of the environment, is due to such things as, frictional engagement of the elastomer with one or more of the stator 14, the rotor 18 and the mud 26, and to hysteresis energy, in the form of heat, developed in the elastomer 22 during operation of the mud motor 10, for example. This hysteresis energy comes from the difference in energy required to deform the elastomer 22 and the energy recovered from the elastomer 22 as the deformation is released. The hysteresis energy generates heat in the elastomer 22, called heat build-up. It is these additional sources of heat generation within the elastomer 22 that the addition of the nanotubes 42 to the elastomer 22, as disclosed herein, is added to mitigate.

Several parameters effect the additional heat generation, such as, the amount of dimensional deformation that the elastomer 22 undergoes during operation, the frictional engagement between the elastomer 22 and the rotor 18 and an overall length 46 of the mud motor 10, for example. Additional heat generation may be reduced with specific settings of these parameters, and the temperature of the elastomer 22 may be maintainable below specific threshold temperatures. Such settings of the parameters, however, may adversely affect the performance and efficiency of the mud motor 10, for example, by allowing more leakage therethrough, as well as increase operational and material costs associated therewith. Embodiments disclosed herein allow an increase in power density of a mud motor 10 by, for example, having a smaller overall mud motor 10 that produces the same amount of output energy to a bit 50, attached thereto, without resulting in increased temperature of the elastomer 22. Additionally, the mud motor 10, using embodiments disclosed herein, may be able to operate at higher pressures, without leakage between the elastomer 22 and the rotor 18, thereby leading to higher overall motor efficiencies, for example.

The carbon nanotubes 42, disclosed in embodiments herein, are embedded in the elastomer 22, such that, the carbon nanotubes 42 interface with a surface 54 of the elastomer 22. Having the carbon nanotubes 42 interface with the surface 54 allows a decrease frictional engagement to exist between the elastomer 22 and matter that comes into contact with the surface 54, such as, the rotor 18 and the mud 26, for example. Such a decrease in friction can result in a corresponding decrease in heat generation. Additionally, in embodiments of the invention, the presence of the carbon nanotubes 42, embedded within the elastomer 22, decrease the hysteresis energy and heat generation resulting therefrom.

While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. 

1. A downhole mud motor, comprising a stator; a rotor in operable communication with the stator; and a plurality of carbon nanotubes embedded in at least a portion of the stator.
 2. The downhole mud motor of claim 1, wherein the stator includes a polymer.
 3. The downhole mud motor of claim 2, wherein the polymer is positioned between the stator and the rotor.
 4. The downhole mud motor of claim 2, wherein the plurality of carbon nanotubes are configured to increase heat transfer through the polymer.
 5. The downhole mud motor of claim 2, wherein the plurality of carbon nanotubes are configured to increase heat transfer from the polymer to matter that comes into contact therewith.
 6. The downhole mud motor of claim 2, wherein the plurality of carbon nanotubes interface with a surface of the polymer to reduce friction between the polymer and matter engagable therewith.
 7. The downhole mud motor of claim 2, wherein the plurality of carbon nanotubes decreases heat generated related to deformation of the polymer.
 8. The downhole mud motor of claim 1, wherein the plurality of carbon nanotubes allows the downhole mud motor to have a greater power density.
 9. A method of improving durability of a mud motor stator, comprising: dissipating heat through the mud motor stator with carbon nanotubes embedded in at least a portion of the stator; and maintaining temperature of the mud motor stator below a threshold temperature.
 10. The method of improving durability of a mud motor stator of claim 9, further comprising: interfacing a surface of at least a portion of the mud motor stator with the carbon nanotubes; and decreasing friction between the surface and matter in contact therewith.
 11. The method of improving durability of a mud motor stator of claim 9, further comprising decreasing heat generated in relation to deformation of at least a portion of the mud motor stator with the carbon nanotubes embedded therein.
 12. The method of improving durability of a mud motor elastomer of claim 9, wherein the at least a portion of the stator is an elastomer.
 13. The downhole mud motor of claim 2, wherein the carbon nanotubes are embedded in the polymer.
 14. The downhole mud motor of claim 2, wherein the polymer is an elastomer. 